The chemistry of metal-dithiolate complexes and metal disulfide complexes will be studied as model systems for metallo-thiolate electron transport proteins such as the ubiquitous iron-sulfur proteins. It is proposed that these metalloproteins can obtain additional reducing power by the formation partial S.S bonds through interaction of two adjacent metal-bound thiolates. Evidence for this hypothesis comes from a number of examples of metal-thiolate complexes where the S.S separations are considerably smaller than the predicted nearest neighbor contact of non-bonded sulfur atoms. Metallosulfur complexes will be synthesized where the dithiolate/disulfide couple is reversible. Dithiolate complexes will be prepared with high-valent metal ions while disulfide complexes will be prepared with low-valent metal ions. The oxidation of the thiolate complexes and the reduction of the disulfide complexes will be studied in order to provide further evidence for the dithiolate/disulfide couple serving as a source of increased reducing power in electron transfer proteins.